"Jim Lesurf" wrote in message
...

Eh? My CRT TV switches both. It switches between 16:9 and 4:3 - by
altering
the horizontal scan width. It switches also for PAL/NTSC. No idea where
you
got the idea that CRT TV "never had" this after 405 line. Not all do, I
guess, but I doubt my set is unique!

The widescreen sets that I have experience of switch between 16:9 and 4:3 by
time-compressing 4:3 video in the digital process area rather than altering
the scan width. Once the digital box is present it's cheaper to do
it that way. But if your set does it by altering the scan width then clearly
not *all* do it digitally. OK, I'll rephase my remark as "Since the end of
405-line transmissions 4:3 TV sets (as opposed to computer monitors) have
never had switching for horizontal scan frequency or width".

Switching between PAL & NTSC doesn't require any change to the horizontal
scan, only the switch between 50 & 60 Hz vertical scan.

Quite a lot can switch the vertical frequency between 50 and 60Hz and a
few have a vertical scan amplitude switching for letterbox presentation
of widescreen material.


You classify operating two or three analogue switches for the two scan
waveforms as "digital processing" in the same sense as the digital domain
*image* processing that pixel displays carry out?

I certainly do not! By digital processing I mean that the image shape is
changed by manipulating the image data. The video processing (colour
decoding, Y/C delay equalisation etc.) has been done digitally in all but
the cheapest sets for quite a few years now, so it doesn't add much to the
cost
of that to add image size/shape conversion as well.


Can't say that treating
those as being the same makes much sense to me.

It wouldn't to me either, if that was what I meant.

Partilularly as I'm not
clear that much "digital" would be needed to switch aspects and scan rates
on a CRT TV.

It's not "needed" it's just cheaper, as any switching associated with the
horizontal scan is expensive.

But it isn't the faffing about needed to convert the pixel number/layout
(which is in effect standards conversion) that causes the long delays
that cause lip-sync problems, rather that is due to more fundamental
aspects of the way flat-screen displays work.

That may be so, if you mean how the makers have *designed* them to work.
Including the use of numbers of pixel rows/columns that don't match the
image,

It really doesn't take long to convert from one image dimension to another,
the added delay is measured in hundreds of microseconds, not milliseconds.
You certainly won't notice that delay on lip-sync

David.